The present invention is directed to carburetor components and carburetors. More particularly, the invention is directed to carburetors capable of providing accurate mixture control, and of thoroughly atomizing fuel air mixtures, thereby leading to uniformity in the distribution of fuel and air to the cylinders of a multi cylinder engine.
It is known that when a piston engine is operated at fuel to air ratios leaner than stoichiometric, the levels of NO.sub.x, HC and CO in the engine exhaust gases are reduced. Since NO.sub.x, HC and CO are generally considered to be the most harmful components of automotive exhaust gases, operation at leaner than stochiometric mixture is a desireable objective from the standpoint of controlling pollution. Unfortunately, when piston engines are operated with fuel to air ratios leaner than stochiometric, such engines generally become considerably more sensitive to deviations from uniform distribution of fuel and air. Thus, when carbureted engines are adjusted for an overall fuel to air ratio substantially leaner than stochiometric, it has been found that some cylinders run leaner than others, some running sufficiently lean to cause misfiring of the engine.
The root of the problem is inadequate atomization and distribution of the fuel in the carburetor. A portion of the fuel, not successfully dispersed in the air passing through the carburetor, can follow various paths along the internal surfaces of the carburetor and being preferentially directed to certain of the cylinders and then to the other cylinders either at the same or different throttle settings. Thus some cylinders run at a richer mixture at the expense of others. The difficulties involved in solving this problem are illustrated by the tremendous number of different carburetor configurations which have been designed with the objective of obtaining more uniform fuel distribution. That the problem has not been satisfactorily solved is also shown by the extent to which the usual principles of carburetor design have been abandoned in recent attempts to solve the problem. A case in point is the "Dresserator" a venturi valve fuel/air mixing device which seeks to attain supersonic velocity in a throat of variable cross-sectional area, and to meter fuel into the throat in proportion to that area as it increases and decreases.
Viewed against the above background, the improved results provided by the present invention, including smooth engine operation with extremely low emissions, operation at leaner than stochiometric mixtures without misfiring but with optimum fuel economy, are surprising and unexpected. A test vehicle with a conventional engine and equipped with a carburetor in accordance with the invention has met the 1976 emissions requirements of both the United States Federal Government and the State of California without a catalytic converter or any other emission control devices.